| Title: |
Does cannabidiol reduce the adverse effects of cannabis in schizophrenia? A randomised, double-blind, cross-over trial |
| Authors: |
Edward Chesney, Dominic Oliver, Ananya Sarma, Ayşe Doğa Lamper, Ikram Slimani, Millie Lloyd, Alex M. Dickens, Michael Welds, Matilda Kråkström, Irma Gasparini-Andre, Matej Orešič, Will Lawn, Natavan Babayeva, Tom P. Freeman, Amir Englund, John Strang & Philip McGuire |
| Year: | 2025 |
| Journal: |
Neuropsychopharmacology |
A new clinical trial published in Neuropsychopharmacology explored whether cannabidiol (CBD) can reduce the short-term negative effects of cannabis (THC) in people with schizophrenia. While cannabis use is known to potentially worsen psychotic symptoms and impair memory in this population, some previous research in healthy individuals suggests that CBD might attenuate these effects.
In this randomized, double-blind, placebo-controlled crossover study, 30 participants with schizophrenia or schizoaffective disorder and a cannabis use disorder received either a single oral dose of CBD (1000 mg) or placebo. Three hours later, they inhaled vaporized cannabis containing a high dose of THC (20–60 mg). Researchers then measured memory performance and psychotic symptoms.
Surprisingly, the results showed that CBD did not protect against cannabis-related harms. In fact, participants who received CBD performed worse on a verbal memory test and experienced a greater increase in positive psychotic symptoms—such as delusions or hallucinations—compared to when they received placebo. Blood levels of THC were unaffected by CBD.
These findings suggest that, in this population, CBD may not lessen—and could potentially worsen—the acute effects of THC. While the sample was small and the study examined only short-term outcomes, the results raise important questions about the role of CBD in managing cannabis-related risks for people with schizophrenia.
Read the full publication here.
Citation: Chesney, E., Oliver, D., Sarma, A. et al. Does cannabidiol reduce the adverse effects of cannabis in schizophrenia? A randomised, double-blind, cross-over trial. Neuropsychopharmacol. (2025). https://doi.org/10.1038/s41386-025-02175-3